Estimation of genetic and non-genetic factors for production and reproduction traits influence conception rate in Holstein cows
Linear animal model was used to estimate (co)variance components and genetic parameter for conception rate and traits related to. The traits included are: days to first service (DFS), open days (OD), number of insemination to conception (INS), success to first insemination (SF), calving interval (CI), days in milk (DIM) and milk yield over 305-d lactation (MY). A total of 170172 records in parity 2 to 6 from 66074 cows from 1978 to 2008 were used. With use of GLM procedure in SAS software (9.2) fixed effects that be effected of these traits were identified. Bivariate linear models were used in the Restricted Maximum Likelihood (REML) method with DMU software to estimate genetic parameters. Estimated heritabilities for reproductive traits were low (below 0.1); also estimated genetic variance component was the lowest for success in first insemination (0.004 ± 0.0005) and was the highest for number of insemination per conception (161.87 ± 17.83) among these traits. Estimated heritabilities for reproductive traits were higher than milk yield over 305-d lactation. Genetic correlations estimated between conception rate and fertility traits were more than milk yield. The results from current study showed that conception rate is a complex trait that highly affected by production traits and milk yield, therefore several measurements related to fertility and production traits should be combined for selection purposes.